Urinals and other drains typically include a seal to contain gases and odors that develop in the drain system. Typical seals include the well known P-traps or S-traps, in which a residual portion of water forms a seal that effectively locks in odors downstream of the seal. Because the seal's upward surface communicates freely with the environment, it generally requires frequent flushing to prevent odors emanating from the seals. Unfortunately, the need for frequent flushing can consume large amounts of water, which can be problematic especially in areas with limited or no access to water.
To eliminate the need for a trap seal in urinals, various types of waterless urinals have been implemented that minimizes the amount of water used. One type of waterless urinals utilizes cartridges having a low-density sealant that floats on a body of trapped residual urine. The seal serves as an odor barrier by allowing urine to permeate through the sealant while preventing downstream odors from emanating through the seal. Such cartridges are described in U.S. Pat. No. 5,711,037 to Reichardt et al., U.S. Pat. No. 6,053,197 to Gorges, U.S. Pat. No. 6,644,339 to Gorges et al., U.S. Pat. No. 6,959,723 to Gorges, and U.S. Pat. No. 6,973,939 to Gorges et al. Unfortunately, the low-density sealant is open to the atmosphere, and odors can permeate through the seal as the sealant becomes depleted. In addition, these cartridges require periodic replacement, adding significantly to the waterless urinals' cost especially in high traffic areas such as airports and stadiums. Furthermore, the used cartridges are often hazardous and generally require a special tool, gloves, and masks for removal.
Instead of chemical sealants, it is known to utilize a duck bill valve, such as those described in U.S. Pat. No. 6,401,266 to Mitchell et al.; U.S. Pat. Appl. No. 2006/0010565 to Cummings (publ. May 2006); U.S. Pat. Appl. No. 2006/0207005 to Janssen (publ. September 2006); and WIPO Patent Appl. No. 2009/040524 to McAlpine (publ. April 2009). However, the duck bill valves typically retain a small amount of fluid after each use leading to odors, and are prone to freezing in cold regions, and sticking. In addition, such systems utilize only a single duck bill valve, which can be problematic if the valve is stuck open due to sticking, freezing, debris, or otherwise.
It is also known to use an umbrella valve in a urinal, such as that described in U.S. Pat. No. 4,180,875 to Wilson. However, the Wilson system is problematic as the system also utilizes a single valve and lacks a removable core, which increases the time and cost for cleaning and maintenance of the system.
While other types of fluid check valves are known, such as that described in U.S. Pat. No. 2,912,999 to Kersh, the valves lack downwardly-sloping valve seats to help protect against backflow from the drain.
Thus, there is still a need for a device having at least two valves capable of operating in a closed system without the need for a chemical sealant.